Nobody Understands Quantum Mechanics. Everybody Uses It.

Table of ContentsWhat Feynman Actually MeantThe Most Tested Theory in the History of ScienceA Century of Quiet Quantum EngineeringWhat We Genuinely Don’t UnderstandThe Mystery Never Touches the MachinesWhat I Told the Director

A few days ago, in a boardroom, a director interrupted my briefing on quantum technology with an accusation. “You’re asking us to bet money,” he said, “on something that, by your own admission, nobody in the world understands. Richard Feynman said so himself.”

He wasn’t being hostile. He was doing his job. Directors are supposed to challenge people who show up asking for budget, and he had done his homework: Feynman really did say, in a 1964 lecture at Cornell, “I think I can safely say that nobody understands quantum mechanics.” The line appears in The Character of Physical Law, and it may be the most quoted sentence any physicist has uttered in the past century.

I’ve heard versions of this challenge for years, in boardrooms, at conferences, and lately at dinner tables. This latest one just happened to arrive the same week I decided the objection finally deserves a full written answer.

Here is what I told the director, and what I want to unpack properly in this article: he was conflating two completely different meanings of the word “understand.” In one sense, Feynman was right, and the situation has barely changed in sixty years. In the other sense, quantum mechanics is the best-understood, most rigorously tested, most economically consequential theory in the history of science. Your phone works because of it. So does the MRI machine that found your friend’s tumor, the GPS constellation that routed your taxi, the laser that carried this article to your screen through a fiber under the ocean, and the flash memory it’s stored on.

The confusion between these two meanings does real damage. I meet intelligent, accomplished people who have quietly filed quantum computing in the same mental drawer as astrology, because they’ve abs…